Electronic systems often use a differential signal pair to transport signals accurately across a printed wiring board or an electronic bus. The use of a differential signal permits the easy removal of noise that may have been added while the signal made its way through a busy wiring board or bus. Once the differential signal has arrived at its destination, a single-ended signal will need to be derived from it, because most electronic functions are implemented using signals that are referenced to a common ground.
FIG. 5 shows a conventional differential to single-ended (DS) circuit 504, that translates a differential signal pair into a single-ended output. In digital electronic systems, the single-ended signal digital should ideally have the same duty cycle as the differential signal pair. The duty cycle requirement means that the time interval Tdiff between any two consecutive crossings of the differential signal pair, is equal to a corresponding time interval Tsingle between two consecutive transitions of the single-ended signal.
Unfortunately, the ideal differential to single-ended translation described above cannot be achieved in practice. Non-idealities in manufactured circuits, and the sensitivity of such circuits to temperature and power supply variations, prevent the single-ended signal from having the exact duty cycle as the differential signal pair. As a result, the single-ended signal obtained by conventional DS circuits is skewed when compared to the differential signal pair.
A limited solution to the skew problem has been to better control the manufacturing process to yield DS circuits that are structurally more consistent. Despite such attempts, most digital circuit designers take the conservative approach and will design their digital circuitry to tolerate a certain amount of skew in the single-ended signals that are derived from a differential signal pair. This may be a proper precaution because even if the manufacturing process could be accurately controlled, it still does not eliminate the skew caused by the sensitivity of the conventional DS circuit 504 to power supply or temperature variations. Therefore, there is a need to minimize the skew resulting from a conventional DS circuit.